Postsilicon Oxide Etch Cleaning Process Using Integrated Ashing and an HF Vapor Process

Abstract

A totally integrated dry cleaning process after silicon oxide etching in fluorocarbon gases was proposed and demonstrated on blanket silicon oxide film and patterned wafers. Silicon oxide etching was performed using an inductively coupled plasma etcher using 100% gas. In situ oxygen plasma and HF vapor were used for cleaning fluorocarbon polymeric contamination formed during oxide etching. This process sequence was performed in a vacuum cluster system in our laboratory. With the apparatus, we have the ability to transfer samples between processing chambers and perform surface analysis at a base pressure in the range. In this manner, we can mimic a clustered process, avoid ambient contamination, and obtain an accurate picture of the evolution of the wafer surface throughout the process sequence. We support our cleaning results with quasi-in situ angle-resolved X-ray photoelectron spectroscopy. It was demonstrated that planar surfaces after silicon oxide etching could be cleaned, leaving less than one monolayer of oxygen, fluorine, and carbon on the surface. The proposed cleaning process was also successful in removing contamination from both sidewalls and trench bottom in line- and space-patterned samples. The measured contact resistance values after the cleaning process were close to the theoretical minimum.